Cellulose nanofibrils are easily obtained from trees, for which each single cellulose fiber is composed of tens of millions smaller fibers, called "fibrils. There are several ways to separate these from the fibers, and the research team developed a process to rebind these fibrils together into new fibers with controlled mechanical properties.[4] Says study coauthor, Fredrik Lundell, an associate professor of mechanics at KTH,

"We have taken out fibrils from natural cellulose fibers... then we have assembled fibrils again into very strong filament. It is about 10 to 20 microns thick, much like a strand of hair."[4]

The research team was able to produce such fibers with a specificultimate strength considerably higher than previously reported cellulose filaments. Specific strength is the strength normalized to a per weight basis.[4] On such a per weight basis, these fibers can be stronger than steel or aluminum. Such strength arises from the process used in making the filaments, which achieves an alignment of the nanofibrils on a nanoscale.[3]

Some representative mechanical properties of cellulose filaments for several different processing cases are shown in the following table.[3]

The material is environmentally friendly in another way. Since the mechanical properties of the filaments can be controlled, they can be made flexible. When the fibrils are perfectly aligned in the thread, there's high strength, but misalignment allows flexibility. Trees do this naturally, letting some parts, such as branches, to bend in the wind rather than breaking. Flexible cellulose filaments could substitute for cotton in clothing.[4]

In a world where we've reached peak oil and possible peaks in the production of various other raw materials, some believe that we're close to reaching peak cultivation of cotton.[4] Additionally, says Lundell,

"Cotton cultivation requires large amounts of water... Take for example the Aral Sea, which more or less disappeared as a result of the cultivation of cotton in Asia. If we are to have a 100 percent sustainablesociety then we need more materials that have a natural place in the natural cycle."[4]